This invention relates to a miniaturized, programmable radiation source for use in delivering substantially constant or intermittent levels of x-rays to a specified region and, more particularly, to an apparatus for delivering a controlled dose of radiation to a localized volume of tissue, such as a volume of tissue of the human body.
In the field of medicine, radiation is used for diagnostic, therapeutic and palliative treatment of patients. The conventional medical radiation sources used for these treatments include large fixed position machines such as linear accelerators ("LINACs"), smaller transportable radiation delivery machines such as high-dose-rate after loaders, and catheters for low-dose-rate brachytherapy. The current state of the art treatment systems utilize computers to generate complex treatment plans for treating complex geometric volumes.
Typically, these systems apply doses of radiation in order to inhibit the growth of new tissue because it is known that radiation affects dividing cells more than the mature cells found in non-growing tissue. Thus, the regrowth of cancerous tissue in the site of an excised tumor can be treated with radiation to prevent the recurrence of cancer. Alternatively, radiation can be applied to other areas of the body to inhibit tissue growth, for example the growth of new blood vessels inside the eye that can cause macular degeneration.
Conventional radiation treatments systems, such as the LINAC used for medical treatment, utilize a high power remote radiation source and direct a beam of radiation at a target area, such as tumor inside the body of a patient. This type of treatment is referred to as teletherapy because the radiation source is located a predefined distance, approximately one meter, from the target. This treatment suffers from the disadvantage that tissue disposed between the radiation source and the target is exposed to radiation.
An alternative treatment system utilizing a point source of radiation is disclosed in U.S. Pat. Nos. 5,153,900 issued to Nomikos et al., 5,369,679 to Sliski et al., and 5,422,926 to Smith et al., all owned by the assignee of the present application, all of which are hereby incorporated by reference. The system includes a miniaturized, insertable probe capable of producing low power radiation in predefined dose geometries disposed about a predetermined location. This treatment is referred to as brachytherapy because the source is located close to or in some cases within the area receiving treatment. One advantage of brachytherapy is that the radiation is applied primarily to treat a predefined tissue volume, without significantly affecting the tissue in adjacent volumes.
Typical radiation therapy treatment involves positioning the insertable probe into or adjacent to the tumor or the site where the tumor or a portion of the tumor was removed to treat the tissue adjacent the site with a "local boost" of radiation. In order to facilitate controlled treatment of the site, it is desirable to support the tissue portions to be treated at a predefined distance from the radiation source. Alternatively, where the treatment involves the treatment of surface tissue or the surface of an organ, it is desirable to control the shape of the surface as well as the shape of the radiation field applied to the surface.
The treatment can involve the application of radiation, either continuously or intermittently, over an extended period of time. Therefore, it is desirable that the insertable probe be adjustably supported in a compliant manner to accurately position the radiation source with respect to the treated site and accommodate normal minor movements of the patient, such as movements associated with breathing.
In practice, the application of X-radiation to target tissue requires precise positioning of the X-ray source with respect to the target tissue, and maintaining that relative positioning throughout treatment. For therapeutic treatment of brain tumors using X-ray probes generally of the type disclosed in U.S. Pat. No. 5,153,900, stereotactic frames affixed to the patients skull are often used to effect the required relative positioning, as disclosed in U.S. Pat. No. 5,369,679. For treatment to other body parts, the user must otherwise support the relatively miniature X-ray probe. Such positioning using manual techniques has proven to be quite difficult.
Accordingly, it is an object of the present invention to provide an improved system for delivering radiation to a localized area. It is another object to provide an improved system for establishing and maintaining a desired position for therapeutic X-ray source.